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Inline filter BEFORE or AFTER pump

Electric pumps don't like to pull, they push. A restrictive filter before the pump can dramatically shorten pump life. The normal setup would be a coarse filter before the pump to prevent pump damage and a fine filter at the engine to keep the fines out of the carb/injectors. Typical would be a 100-300 micron filter before the pump, 10-40 micron before the carb. You can get inexpensive washable filters on Ebay that last a lifetime. Its a good investment, especially as fast as modern fuel rusts out fuel tanks.
 
There are two distinct types of electric pump - gravity feed and suction. e.g. Mini, for example, had the pump below the petrol tanks on the rear subframe (gravity), a lot of other cars had the pump on the engine compartment bulkhead - suction all the way from the rear tank. Agree with the coarse/fine idea though.
 
Suppose they technically do have a coarse filter before the pump, well mine has stainless mesh basket brazed over the pickup pipe in the tank
 
DarrenH said:
Despite seeming illogical, most oem setups filter the fuel AFTER the pump.

My series 3 with glass sediment bowl is, my ninety with facet redtop was after, my other fuel injected cars are after

I wonder why?

Maybe because pumps are quite robust even with high levels of particulates, while the fuel metering system is not, filter after protects the system from the actual pump introducing debris. Positive displacement electric pumps, fuel flows through the armature of the motor itself!!
Click to expand...

The fuel pickup has a mesh filter to stop big chucks and the pump is usually a small centrifugal type, they are not that picky on particles. If you suspend sand in water it will happily pump it (to an extend ofcourse).
injectors or jets however are a lot smaller and will have troubles with it.

Plus if you put a filter in front of the pump, especially with petrol, you run the risk of cavitation. Moreso if the filter gets clogged. Not to mention efi pumps are mostly located in the tank, which would mean changing the filter gets complicated.

source: just my random thoughts.
 
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